JP7058909B2 - Belt type continuously variable transmission control device - Google Patents

Description

The present invention relates to a control device for a belt-type continuously variable transmission mounted on a vehicle.

Conventionally, as a belt wound around a primary pulley and a secondary pulley, a chain belt type continuously variable transmission using a chain belt in which a large number of links are annularly connected by pins has been described (see, for example, Patent Document 1). ).

Japanese Unexamined Patent Publication No. 2016-20197

In the above-mentioned conventional device, the input torque from the engine is constant during coast deceleration by depressing the brake operation, but the required thrust increases as the gear ratio becomes lower due to the low return control of the gear ratio accompanying deceleration. Therefore, during the low return control in the coast state, the secondary hydraulic pressure is controlled to be increased so as to suppress the belt slip in the shift hydraulic pressure control. Therefore, when the coast is decelerated by depressing the brake, the pin end surface of the chain belt and the pulley sheave surface collide with each other due to a high contact force, and this contact collision is repeated due to the winding movement of the chain belt, which causes chain noise. was there.

The present invention has been made focusing on the above problems, and an object of the present invention is to provide a control device for a belt-type continuously variable transmission capable of suppressing the generation of chain noise during coast deceleration due to a brake depression operation. ..

In order to achieve the above object, the present invention includes a belt-type continuously variable transmission and a transmission controller that controls the secondary pressure led to the secondary pulley of the belt-type continuously variable transmission based on the transmission input torque.
The belt-type continuously variable transmission is arranged between the drive source for traveling and the drive wheels, and has a primary pulley, a secondary pulley, and a chain belt spanned on the sheave surface of the primary pulley and the sheave surface of the secondary pulley. Have.
The speed change controller is set to a lower hydraulic pressure as the vehicle deceleration increases during coast deceleration by depressing the brake, and calculates the upper limit hydraulic pressure at which the sound vibration performance is at an allowable level, and the secondary pressure is set to be less than or equal to the upper limit hydraulic pressure. It has a secondary pressure limiting control unit that limits the pressure.

As a result, it is possible to suppress the generation of chain noise during coast deceleration due to the operation of stepping on the brake.

It is an overall system diagram which shows the drive system and the control system of the engine vehicle to which the control device of the belt type continuously variable transmission of Example 1 is applied. It is a shift schedule diagram which shows an example of the D range stepless shift schedule used when the stepless shift control in an automatic shift mode is executed by a variator. FIG. 3 is a schematic configuration diagram showing a coordinated control configuration of a belt-type continuously variable transmission, an engine, and a brake according to the first embodiment. It is a flowchart which shows the flow of the secondary pressure limit control process at the time of brake ON coast deceleration executed by the secondary pressure limit control unit of the CVT control unit of Example 1. FIG. In Example 1, the time indicating the characteristics of the accelerator, brake, vehicle speed, engine speed Ne, turbine speed Nt, lockup torque Tlu, engine torque Te, brake torque Tb, gear ratio, and secondary pressure during brake ON coast deceleration. It is a chart.

Hereinafter, embodiments for implementing the control device for the belt-type continuously variable transmission of the present invention will be described with reference to Example 1 shown in the drawings.

The control device in the first embodiment is applied to an engine vehicle equipped with a belt-type continuously variable transmission (an example of an automatic transmission) composed of a torque converter, a forward / backward switching mechanism, a variator, and a final deceleration mechanism. Hereinafter, the configuration of the first embodiment will be described separately by dividing it into an "overall system configuration", a "coordinated control configuration of a belt-type continuously variable transmission, an engine and a brake", and a "secondary pressure limit control processing configuration during brake ON coast deceleration". do.

[Overall system configuration]
FIG. 1 shows a drive system and a control system of an engine vehicle to which the control device of the first embodiment is applied. Hereinafter, the overall system configuration will be described with reference to FIG.

As shown in FIG. 1, the drive system of the engine vehicle includes an engine 1, a torque converter 2, a forward / backward switching mechanism 3, a variator 4, a final deceleration mechanism 5, and drive wheels 6 and 6. There is.
Here, the belt-type continuously variable transmission CVT is configured by incorporating a torque converter 2, a forward / backward switching mechanism 3, a variator 4, and a final deceleration mechanism 5 in a transmission case (not shown).

The engine 1 can control the output torque by an engine control signal from the outside in addition to the control of the output torque by the accelerator operation by the driver. The engine 1 has an output torque control actuator 10 that performs torque down control by ignition timing retard control, throttle valve open / close control, and the like.

The torque converter 2 is a starting element with a fluid coupling having a torque increasing function and a torque fluctuation absorbing function. It has a lockup clutch 20 capable of directly connecting the engine output shaft 11 (= torque converter input shaft) and the torque converter output shaft 21 when the torque increasing function or the torque fluctuation absorbing function is not required. The torque converter 2 is provided with a pump impeller 23 connected to the engine output shaft 11 via a converter housing 22, a turbine runner 24 connected to the torque converter output shaft 21, and a one-way clutch 25 in the case. The stator 26 is a component.

The forward / backward switching mechanism 3 is a mechanism that switches the input rotation direction to the variator 4 between a forward rotation direction during forward travel and a reverse rotation direction during reverse travel. The forward / backward switching mechanism 3 has a double pinion type planetary gear 30, a forward clutch 31 with a plurality of clutch plates, and a reverse brake 32 with a plurality of brake plates. The forward clutch 31 is hydraulically engaged by the forward clutch pressure Pfc when the forward traveling range such as the D range is selected. The reverse brake 32 is hydraulically fastened by the reverse brake pressure Prb when the reverse travel range such as the R range is selected. The forward clutch 31 and the reverse brake 32 are both released by draining the forward clutch pressure Pfc and the reverse brake pressure Prb when the N range (neutral range) is selected.

The variator 4 has a primary pulley 42, a secondary pulley 43, and a chain belt 44, and the gear ratio (ratio of variator input rotation and variator output rotation) is steplessly changed by changing the belt contact diameter. Equipped with a shifting function. The primary pulley 42 is composed of a fixed pulley 42a and a slide pulley 42b arranged coaxially with the variator input shaft 40, and the slide pulley 42b is a primary pressure Ppri in which the discharge pressure from the oil pump 70 is guided to the primary pressure chamber 45. Slides with. The secondary pulley 43 is composed of a fixed pulley 43a and a slide pulley 43b arranged coaxially with the variator output shaft 41, and the slide pulley 43b is a secondary pressure Psec in which the discharge pressure from the oil pump 70 is guided to the secondary pressure chamber 46. Slides with. The chain belt 44 is hung on the V-shaped sheave surface of the primary pulley 42 and the V-shaped sheave surface of the secondary pulley 43. The chain belt 44 is a chain type belt in which a large number of chain elements arranged in the pulley traveling direction are connected by pins penetrating in the pulley axial direction.

The final deceleration mechanism 5 is a mechanism that decelerates the rotation of the variator output from the variator output shaft 41, gives a differential function, and transmits the differential function to the left and right drive wheels 6 and 6. As a reduction gear mechanism, the final deceleration mechanism 5 includes an output gear 52 provided on the variator output shaft 41, an idler gear 53 and a reduction gear 54 provided on the idler shaft 50, and a final provided at the outer peripheral position of the differential case. It has a gear 55 and. Further, as a differential gear mechanism, it has a differential gear 56 interposed between the left and right drive shafts 51 and 51.

As shown in FIG. 1, the control system of an engine vehicle includes a hydraulic control unit 7 representing a hydraulic control system, a CVT control unit 8 representing an electronic control system, and an engine control unit 9.

The hydraulic control unit 7 controls the primary pressure Ppri guided to the primary pressure chamber 45, the secondary pressure Psec guided to the secondary pressure chamber 46, the forward clutch pressure Pfc to the forward clutch 31, the backward brake pressure Prb to the reverse brake 32, and the like. It is a unit that regulates pressure. The hydraulic pressure control unit 7 includes an oil pump 70 that is rotationally driven by an engine 1 that is a driving drive source for traveling, and a hydraulic pressure control circuit 71 that regulates various control pressures based on the discharge pressure from the oil pump 70. .. The hydraulic control circuit 71 includes a line pressure solenoid valve 72, a primary pressure solenoid valve 73, a secondary pressure solenoid valve 74, a select solenoid valve 75, and a lockup pressure solenoid valve 76. The solenoid valves 72, 73, 74, 75, 76 adjust to each command pressure according to the control command value output from the CVT control unit 8.

The line pressure solenoid valve 72 adjusts the discharge pressure from the oil pump 70 to the commanded line pressure PL according to the line pressure command value output from the CVT control unit 8. This line pressure PL is the original pressure when adjusting various control pressures, and is a hydraulic pressure that suppresses belt slip and clutch slip with respect to the torque transmitted to the drive system.

The primary pressure solenoid valve 73 adjusts the pressure reduction to the primary pressure Ppri commanded with the line pressure PL as the original pressure according to the primary pressure command value output from the CVT control unit 8. The secondary pressure solenoid valve 74 adjusts the pressure reduction to the secondary pressure Psec commanded with the line pressure PL as the original pressure according to the secondary pressure command value output from the CVT control unit 8.

The select solenoid valve 75 adjusts the pressure reduction to the forward clutch pressure Pfc or the backward brake pressure Prb commanded with the line pressure PL as the original pressure according to the forward clutch pressure command value or the reverse brake pressure command value output from the CVT control unit 8. do.

The lock-up pressure solenoid valve 76 adjusts the lock-up control pressure PL / U for engaging / slip-engaging / releasing the lock-up clutch 20 according to the lock-up pressure command value output from the CVT control unit 8.

The CVT control unit 8 performs line pressure control, shift control, forward / backward switching control, lockup control, and the like. In the line pressure control, a command value for obtaining a target line pressure according to the accelerator opening or the like is output to the line pressure solenoid valve 72. In the shift control, when the target gear ratio (target primary rotation Npri ^* ) is determined, the command value for obtaining the determined target gear ratio (target primary rotation Npri ^* ) is output to the primary pressure solenoid valve 73 and the secondary pressure solenoid valve 74. In the forward / backward switching control, a command value for controlling engagement / release of the forward clutch 31 and the reverse brake 32 is output to the select solenoid valve 75 according to the selected range position. In the lockup control, a command value for controlling the lockup control pressure PL / U that engages / engages / releases the lockup clutch 20 is output to the lockup pressure solenoid valve 76.

The CVT control unit 8 includes a primary rotation sensor 80, a vehicle speed sensor 81, a secondary pressure sensor 82, an oil temperature sensor 83, an inhibitor switch 84, a brake switch 85, an accelerator opening sensor 86, a primary pressure sensor 87, and a secondary rotation sensor 88. Sensor information and switch information from the turbine rotation sensor 89 and the like are input. Further, engine rotation speed information from the engine rotation sensor 12 is input to the engine control unit 9.

The CVT control unit 8 and the engine control unit 9 are connected by a CAN communication line 13 so as to be capable of bidirectional communication. For example, engine torque information and the like are input from the engine control unit 9 to the CVT control unit 8 via the CAN communication line 13. A fuel cut request, a fuel recover request, and the like are transmitted from the CVT control unit 8 to the engine control unit 9 via the CAN communication line 13.

FIG. 2 shows an example of a D-range continuously variable transmission schedule used when the variator 4 executes continuously variable transmission control in the automatic transmission mode when the D-range is selected.

The "D range shift mode" is an automatic shift mode that automatically and steplessly changes the gear ratio according to the driving state of the vehicle. The shift control in the "D range shift mode" is the operation point on the D range continuously variable transmission schedule of FIG. 2 specified by the vehicle speed VSP (vehicle speed sensor 81) and the accelerator opening APO (accelerator opening sensor 86). VSP, APO) determines the target primary rotation speed Npri ^* . Then, the pulley hydraulic control is performed to match the primary rotation speed Npri from the primary rotation sensor 80 with the target primary rotation speed Npri ^* .

That is, as shown in FIG. 2, the D-range continuously variable transmission schedule used in the "D-range continuously variable transmission mode" has a gear ratio range of the lowest gear ratio and the highest gear ratio according to the operating point (VSP, APO). It is set to change the gear ratio steplessly within the range. For example, when the vehicle speed VSP is constant, when the accelerator is depressed, the target primary rotation speed Npri ^* rises and shifts in the downshift direction, and when the accelerator return operation is performed, the target primary rotation speed Npri ^* decreases and rises. Shift in the shift direction. When the accelerator opening APO is constant, the gear shifts in the upshift direction when the vehicle speed VSP increases, and shifts in the downshift direction when the vehicle speed VSP decreases.

The shift line shown by the thick line in FIG. 2 is a coast shift line at the time of accelerator foot release operation in which the accelerator opening APO is zero. For example, when the brake is turned on and the coast is decelerated, as shown by the arrow A in FIG. 2, low return control is performed in which the vehicle is downshifted toward the lowest gear ratio in response to a decrease in the vehicle speed VSP.

[Coordinated control configuration of belt-type continuously variable transmission, engine and brake]
Hereinafter, a coordinated control configuration of the belt type continuously variable transmission, the engine, and the brake will be described with reference to FIG.

As shown in FIG. 3, the drive system of the engine vehicle includes the engine 1, the torque converter 2 (lockup clutch 20), the forward / backward switching mechanism 3 (forward clutch 31, reverse brake 32), the variator 4, and the end. It includes a speed reduction mechanism 5 and a drive wheel 6.

As shown in FIG. 3, the control system of the engine vehicle includes a CVT control unit 8 (shift controller), an engine control unit 9, and a brake control unit 14. These control units 8, 9 and 14 are connected to each other by a CAN communication line 13 capable of exchanging information.

The CVT control unit 8 calculates the upper limit hydraulic pressure at which the chain noise (sound vibration performance) becomes an allowable level based on the vehicle deceleration when the brake is ON and the coast decelerates, and limits the secondary pressure Psec so that it is equal to or less than the upper limit hydraulic pressure. It has a pressure limiting control unit 8a. The secondary pressure limit control unit 8a calculates the lower limit hydraulic pressure that secures the clamping force that suppresses belt slip based on the transmission input torque, and when the upper limit hydraulic pressure ≤ the lower limit hydraulic pressure, the secondary pressure Psec is set to be equal to or higher than the lower limit hydraulic pressure. Restrict.

The accelerator OFF operation information and the switching information from L / U ON to L / U OFF are output from the CVT control unit 8 to the engine control unit 9 by transmission via the CAN communication line 13. Brake ON operation information, switching information from L / U ON to L / U OFF, and the speed ratio of the torque converter 2 are transmitted from the CVT control unit 8 to the brake control unit 14 via the CAN communication line 13. The information that is below the coupling point (Ne-Nt ≥ rotation with a predetermined difference) is output.

The engine control unit 9 starts fuel cut control (fuel cut control) when the accelerator OFF operation information is input from the CVT control unit 8 via the CAN communication line 13. Then, when the switching information of the lockup clutch 20 from L / U ON to L / U OFF is input from the CVT control unit 8 via the CAN communication line 13, the fuel cut recover control is started. The fuel cut recover control is then switched to the fuel cut control when the vehicle is stopped.

When the brake control unit 14 inputs the brake ON operation information from the brake OFF to the brake ON by transmission from the CVT control unit 8 via the CAN communication line 13, the brake torque correction control at the time of L / U ON increases and corrects the brake torque. To start. Then, when the switching information of the lockup clutch 20 from L / U ON to L / U OFF is input from the CVT control unit 8 via the CAN communication line 13, the L / U OFF that reduces the correction amount of the brake torque. When brake torque correction control is started. Further, when the information that the speed ratio of the torque converter 2 is equal to or less than the coupling point by the transmission from the CVT control unit 8 via the CAN communication line 13 is input, the brake torque correction control at the time of L / U OFF is terminated.

Here, the brake torque correction control is performed by inputting the master cylinder pressure generated by the master cylinder 16 by depressing the brake pedal 15 and issuing a control command to the brake hydraulic actuator 17 for increasing, depressurizing, and holding the master cylinder pressure. Will be. The control hydraulic pressure generated by the brake hydraulic actuator 17 is supplied to the drive wheels 6 and the wheel cylinders 18 provided on the driven wheels (not shown).

[Secondary pressure limit control processing configuration during brake ON coast deceleration]
FIG. 4 shows the flow of the secondary pressure limit control process at the time of brake ON coast deceleration executed by the secondary pressure limit control unit 8a of the CVT control unit 8 of the first embodiment. Hereinafter, each step in FIG. 4 will be described.

In step S1, following the start, it is determined whether or not the brake is ON and the coast is decelerating. If YES (during deceleration of the brake ON coast), the process proceeds to step S2, and if NO (not during deceleration of the brake ON coast), the process proceeds to step S11.

Here, "during brake ON coast deceleration" is determined by detecting the brake depressing operation after the accelerator foot release operation is detected. Then, the determination that the brake is ON and the coast is decelerated is set as the start condition of the secondary pressure limit control.

In step S2, following the determination in step S1 that the brake is ON and the coast is decelerating, or the determination that the end condition of the secondary pressure limit control in step S10 is not satisfied, the secondary pressure is based on the transmission input torque. The target hydraulic pressure for Psec is calculated, and the process proceeds to step S3.

Here, the "target hydraulic pressure of the secondary pressure Psec" is a predetermined safety rate based on the transmission input torque (safety rate = transmissible torque when the chain belt 44 is clamped at the secondary pressure Psec / transmission input torque, for example. , Safety rate = about 1.5) is calculated as the hydraulic pressure required to ensure. The transmission input torque is the drive torque from the engine 1 via the torque converter 2 in the drive state due to the accelerator depression operation. In the coastal state due to the accelerator foot release operation, the engine brake torque is applied. In the coast deceleration state due to the brake depression operation, the torque is obtained by adding the brake torque to the engine brake torque.

In step S3, following the calculation of the target hydraulic pressure in step S2, the upper limit hydraulic pressure is calculated based on the vehicle deceleration, and the process proceeds to step S4.

Here, the information of "vehicle deceleration" is acquired from the differential calculation of the vehicle speed VSP, the sensor values of the front and rear G sensors, and the like. The "upper limit hydraulic pressure" is set to the secondary pressure Psec at which the chain noise (sound vibration performance) becomes an allowable level (a magnitude that does not give a sense of discomfort) to the occupant. When the secondary pressure Psec is set to a constant pressure, the chain noise increases as the vehicle deceleration increases. Therefore, the upper limit hydraulic pressure is set to a lower oil pressure as the vehicle deceleration increases.

In step S4, following the calculation of the upper limit hydraulic pressure in step S3, it is determined whether or not the target hydraulic pressure is less than the upper limit hydraulic pressure. If YES (target oil pressure <upper limit oil pressure), the process proceeds to step S5, and if NO (target oil pressure ≥ upper limit oil pressure), the process proceeds to step S6.

In step S5, following the determination that the target hydraulic pressure <upper limit hydraulic pressure in step S4, the target secondary pressure is calculated by adding the shift feedback hydraulic pressure to the target hydraulic pressure, and the process proceeds to step S9.

Here, the "shift feedback hydraulic pressure" refers to the hydraulic pressure component due to the deviation between the target secondary pressure and the actual secondary pressure when the feedback control of the secondary pressure Psec is performed. That is, the secondary pressure Psec is feedback-controlled so as to eliminate the deviation between the target secondary pressure and the actual secondary pressure detected by the secondary pressure sensor 82.

In step S6, following the determination that the target hydraulic pressure ≥ the upper limit hydraulic pressure in step S4, it is determined whether or not the lower limit hydraulic pressure is less than the upper limit hydraulic pressure. If YES (lower limit oil pressure <upper limit oil pressure), the process proceeds to step S7, and if NO (lower limit oil pressure ≥ upper limit oil pressure), the process proceeds to step S8.

Here, the "lower limit hydraulic pressure" is calculated as the hydraulic pressure that secures the clamping force that suppresses the belt slip based on the transmission input torque. That is, the lower limit hydraulic pressure is calculated as the hydraulic pressure for belt slip prevention measures necessary to secure a safety factor lower than the target hydraulic pressure (for example, safety factor = about 1.2) based on the transmission input torque.

In step S7, following the determination that the lower limit hydraulic pressure <upper limit hydraulic pressure in step S6, the target secondary pressure is calculated by adding the shift feedback hydraulic pressure to the upper limit hydraulic pressure, and the process proceeds to step S9.

In step S8, following the determination that the lower limit hydraulic pressure ≥ the upper limit hydraulic pressure in step S6, the target secondary pressure is calculated by adding the shift feedback hydraulic pressure to the lower limit hydraulic pressure, and the process proceeds to step S9.

In step S9, following the calculation of the target secondary pressure in steps S5, S7, and S8, the calculated target secondary pressure is converted into the secondary instruction pressure which is a control command, and the process proceeds to step S10.

In step S10, following the calculation of the secondary instruction pressure in step S9, it is determined whether or not the secondary pressure limit control end condition is satisfied. If YES (secondary pressure limit control end condition is satisfied), the process proceeds to the end, and if NO (secondary pressure limit control end condition is not satisfied), the process returns to step S2.

Here, the "secondary pressure limit control end condition" is a condition for determining whether or not the situation does not require the secondary pressure limit control, and is, for example, the end condition of the brake torque correction control of the torque converter 2. It is given under the condition that the speed ratio is less than or equal to the coupling point.

In step S11, following the determination that the brake is not on and the coast is decelerating in step S1, the normal control of the secondary pressure is executed, and the process proceeds to the end.

Here, the "normal control of the secondary pressure" means a control in which the target hydraulic pressure of the secondary pressure Psec is calculated based on the transmission input torque, and the shift feedback hydraulic pressure is added to the target hydraulic pressure to obtain the target secondary pressure.

Next, the operation of the first embodiment will be described separately for "secondary pressure limit control processing action during brake ON coast deceleration" and "sound vibration countermeasure control action during brake ON coast deceleration".

[Secondary pressure limit control processing action during brake ON coast deceleration]
The secondary pressure limit control processing operation at the time of brake ON coast deceleration will be described with reference to the flowchart of FIG.

In the case of a scene that is not during the brake ON coast deceleration such as a drive driving scene, the process proceeds from step S1 → step S11 → end in the flowchart of FIG. In step S11, the target hydraulic pressure of the secondary pressure Psec is calculated based on the transmission input torque, and the normal control of the secondary pressure as the target secondary pressure by adding the shift feedback hydraulic pressure to the target hydraulic pressure is executed.

When the brake is ON and the coast is decelerating and the target hydraulic pressure is less than the upper limit hydraulic pressure in the start range of the secondary pressure limit control, go to step S1 → step S2 → step S3 → step S4 → step S5 → step S9 in the flowchart of FIG. And proceed. In step S5, the target secondary pressure is calculated by adding the shift feedback oil pressure to the target oil pressure. In the next step S9, the calculated target secondary pressure is converted into the secondary instruction pressure and output as a secondary pressure control command.

After that, when the target hydraulic pressure rises during the secondary pressure limit control and shifts from the target hydraulic pressure <upper limit hydraulic pressure to the target hydraulic pressure ≥ upper limit hydraulic pressure, if the lower limit hydraulic pressure <upper limit hydraulic pressure, step S1 → step S2 → step S3 → step. The procedure proceeds to S4 → step S6 → step S7 → step S9. In step S7, the target secondary pressure is calculated by adding the shift feedback hydraulic pressure to the upper limit hydraulic pressure. In the next step S9, the calculated target secondary pressure is converted into the secondary instruction pressure and output as a secondary pressure control command. The secondary pressure limiting control that limits the increase in the target secondary pressure by the upper limit hydraulic pressure is maintained until the target hydraulic pressure decreases and the target hydraulic pressure ≥ upper limit hydraulic pressure shifts to the target hydraulic pressure <upper limit hydraulic pressure.

After that, when the target hydraulic pressure decreases and the transition from the target hydraulic pressure ≧ upper limit hydraulic pressure to the target hydraulic pressure <upper limit hydraulic pressure, the process again proceeds to step S1 → step S2 → step S3 → step S4 → step S5 → step S9. That is, it returns to the secondary pressure control that controls the target secondary pressure based on the target hydraulic pressure.

Further, it is assumed that the vehicle deceleration is large and the upper limit hydraulic pressure is lowered during the secondary pressure limit control, the target hydraulic pressure <upper limit hydraulic pressure is changed to the target hydraulic pressure ≥ upper limit hydraulic pressure, and the lower limit hydraulic pressure ≥ upper limit hydraulic pressure. In this case, the process proceeds from step S1 → step S2 → step S3 → step S4 → step S6 → step S8 → step S9. In step S8, the target secondary pressure is calculated by adding the shift feedback hydraulic pressure to the lower limit hydraulic pressure. In the next step S9, the calculated target secondary pressure is converted into the secondary instruction pressure and output as a secondary pressure control command. In the secondary pressure limit control that limits the decrease in the target secondary pressure so that it is equal to or higher than the lower limit hydraulic pressure, the vehicle deceleration becomes smaller and the upper limit hydraulic pressure becomes higher, and the lower limit hydraulic pressure ≥ upper limit hydraulic pressure shifts to the lower limit hydraulic pressure <upper limit hydraulic pressure. Will be maintained until.

Then, the secondary pressure limit control at the time of brake ON coast deceleration, which is executed by repeating steps S2 to S10, proceeds to the end and ends when the secondary pressure limit control end condition is satisfied in step S10.

In this way, in the secondary pressure limit control during brake ON coast deceleration, the secondary pressure Psec is in the range of upper limit hydraulic pressure and lower limit hydraulic pressure only during brake ON coast deceleration from the establishment of the start condition to the satisfaction of the end condition. It will be controlled so that it fits inside.

[Control action against sound vibration during brake ON coast deceleration]
As a background, it was pointed out that chain noise was NG in the sensitivity evaluation when the brake was turned on and the coast was decelerated. It was determined that this is because the required thrust increases as the gear ratio shifts to the low gear ratio side even if the input torque is constant when the brake is turned on and the coast is decelerated.

On the other hand, at present, the brake torque correction is switched by turning the lockup clutch ON / OFF when the brake is turned on and the coast is decelerated. That is, when the fuel recover control is performed by releasing the lockup clutch, the absolute value of the input torque becomes small. Therefore, the secondary pressure peaks at the timing of engagement → release of the lockup clutch.

As a measure for lowering the peak of the secondary pressure, the present inventors have released the lockup, and the lockup release determination condition is that the rotation difference between the turbine rotation speed Nt and the engine rotation speed Ne ≤ the predetermined rotation speed (for example, 100 rpm). I tried to take measures against sound vibration by changing.

However, the method of changing the lockup release determination condition has a problem that there is a risk in low vehicle speed rapid braking (ABS non-operation). In particular, it is conceivable that the sudden deceleration during the smooth off of the lockup will be weakened. In addition, there is a problem that there is no difference in rotation and there is a risk that the lockup clutch is switched while it has a capacity.

When considering a solution to the problem, the reason why the secondary pressure is high in the low return control of the gear ratio is that even if the input torque (coast) is constant, the required thrust increases as the gear ratio shifts to the low gear ratio side. .. In addition to this, the hydraulic pressure rise of the low return measures and the shift difference thrust are added to become the secondary pressure.

Therefore, the present inventors have focused on the above-mentioned problems and secondary pressure control, and have limited the secondary pressure Psec to be equal to or less than the upper limit hydraulic pressure in response to the sound vibration request for suppressing chain noise during brake ON coast deceleration. Countermeasure A secondary pressure limiting method was adopted as the secondary pressure. Specifically, without changing the lockup release determination condition, an upper limit is set for the secondary pressure to which the hydraulic pressure increase for low return measures and the shift difference thrust are added in the region before and after the timing when the secondary pressure peaks. However, since there is a risk that the belt capacity will decrease by turning off the hydraulic pressure that the upper limit hydraulic pressure should be secured to the minimum, the following prerequisites are set to prevent the belt from slipping (preventing cliffs from falling).
-The secondary pressure limit control is operated only in the sound vibration countermeasure area (when the brake is ON and the coast is decelerated).
-In the secondary pressure limit control, always maintain the secondary pressure ≥ lower limit oil pressure.

Next, the sound vibration countermeasure control action at the time of brake ON coast deceleration will be described with reference to FIG.
When the accelerator foot release operation is performed at time t1, the fuel cut control for stopping the fuel injection in the engine 1 is started, and the engine torque Te becomes the engine brake torque with a negative value. This engine brake torque is maintained until the time t4 when the lockup release determination condition is satisfied.

When the brake depression operation is performed at time t2, the brake torque correction control at the time of lockup ON, which increases and corrects the brake torque in the brake hydraulic system, is started, and the brake torque becomes a large brake torque due to a negative value. This brake torque is maintained until the time t4 when the lockup release determination condition is satisfied (hatching region rising to the right in FIG. 5).

When the brake depression operation is performed at time t2, the start condition of brake ON coast deceleration is satisfied, and the secondary pressure limit control is started. Then, from time t2 to time t3, where the target hydraulic pressure ≤ the upper limit hydraulic pressure, the secondary pressure is controlled by the target hydraulic pressure.

When the lockup release vehicle speed is reached at time t3, the smooth-off control of the lockup clutch 20 is started. When the target hydraulic pressure> the upper limit hydraulic pressure becomes equal to or before or after this timing, the limitation of the secondary pressure by the upper limit hydraulic pressure is started. The limit of the secondary pressure by this upper limit hydraulic pressure is maintained until the time t5 when the transition from the target hydraulic pressure> the upper limit hydraulic pressure to the target hydraulic pressure ≤ upper limit hydraulic pressure.

When the lockup release condition is satisfied at time t4, that is, the lockup release and the rotation difference (Nt-Ne) ≤ the predetermined rotation speed (for example, 100 rpm), the fuel cut recover control for restarting the fuel injection in the engine 1 is started. To. At the same time, the brake torque correction control in the brake hydraulic system is switched from the brake torque correction control when the lockup is ON to the brake torque correction control when the lockup is OFF. Therefore, from time t2 to time t4, the transmission input torque is the sum of the engine brake torque and the brake torque due to the increase correction, but from time t4 to the time t7, the transmission input torque is based only on the brake torque due to the decrease correction. become.

When the lockup torque Tlu becomes zero at time t6 and the gear ratio of the variator 4 reaches the lowest gear ratio, the turbine rotation speed Nt starts to decrease.

When the turbine rotation speed Nt> engine rotation speed Ne at time t7 and the speed ratio of the torque converter 2 becomes equal to or less than the coupling point, the brake torque correction control at lockup OFF is terminated. At the same time, the secondary pressure limit control ends, and the vehicle stops at time t8.

In this way, when the brake is ON and the coast is decelerated, the normal SEC pressure with a solid peak is limited to the dashed sound vibration countermeasure SEC pressure (upper limit hydraulic pressure) as shown in the in-frame characteristics surrounded by the arrow B in FIG. Will be done. The upper limit hydraulic pressure is set to the secondary pressure at which the chain noise becomes an allowable level. Therefore, when the coast is decelerated by the brake depressing operation, the generation of chain noise is suppressed without changing the lockup release determination condition.

The control device for the belt-type continuously variable transmission CVT of the first embodiment has the effects listed below.

(1) A belt-type continuously variable transmission CVT and a speed change controller (CVT control unit 8) that controls the secondary pressure Psec leading to the secondary pulley 43 of the belt-type continuously variable transmission CVT based on the transmission input torque. Be prepared.
The belt-type continuously variable transmission CVT is arranged between the driving drive source (engine 1) and the drive wheels 6, and has a primary pulley 42, a secondary pulley 43, a sheave surface of the primary pulley 42, and a sheave surface of the secondary pulley 43. The chain belt 44 is hung on the chain belt 44 and the like.
The speed change controller 8 (CVT control unit 8) calculates the upper limit hydraulic pressure at which the sound vibration performance becomes an allowable level based on the vehicle deceleration during coast deceleration by depressing the brake, and sets the secondary pressure Psec to be less than or equal to the upper limit hydraulic pressure. It has a secondary pressure limiting control unit 8a for limiting.
Therefore, it is possible to suppress the generation of chain noise during coast deceleration due to the operation of stepping on the brake.

(2) The secondary pressure limit control unit 8a calculates the lower limit hydraulic pressure that secures the clamping force that suppresses belt slip based on the transmission input torque, and if the lower limit hydraulic pressure is greater than or equal to the upper limit hydraulic pressure, the secondary hydraulic pressure is greater than or equal to the lower limit hydraulic pressure. Limit pressure Psec.
Therefore, it is possible to prevent the chain belt 44 from slipping when the coast is decelerated by the operation of stepping on the brake. That is, when the coast is decelerated by depressing the brake, the secondary pressure Psec is restricted so as not to fall below the lower limit hydraulic pressure.

(3) The secondary pressure limit control unit 8a calculates the target hydraulic pressure that guarantees a predetermined safety factor based on the transmission input torque.
If the target hydraulic pressure is less than the upper limit hydraulic pressure during coast deceleration by stepping on the brake, the secondary indicated pressure is calculated by adding the shift feedback hydraulic pressure to the target hydraulic pressure.
If the lower limit hydraulic pressure is less than the upper limit hydraulic pressure, the secondary indicated pressure is calculated by adding the shift feedback hydraulic pressure to the upper limit hydraulic pressure.
If the lower limit hydraulic pressure is equal to or higher than the upper limit hydraulic pressure, the secondary indicated pressure is calculated by adding the shift feedback hydraulic pressure to the lower limit hydraulic pressure.
Therefore, it is possible to suppress the generation of chain noise and prevent the belt from slipping when the coast is decelerated by depressing the brake. That is, when the coast is decelerated by depressing the brake, the secondary pressure Psec is controlled to the hydraulic pressure within the limited range so as to be equal to or higher than the upper limit hydraulic pressure and the lower limit hydraulic pressure.

(4) The driving drive source is the engine 1, which includes a torque converter 2, an engine controller (engine control unit 9), and a brake controller (brake control unit 14).
The torque converter 2 is arranged between the engine 1 and the belt-type continuously variable transmission CVT, and has a lockup clutch 20.
The engine controller (engine control unit 9) starts fuel cut control when the accelerator foot release operation information is input.
When the brake controller (brake control unit 14) inputs the brake depression operation information, the brake controller (brake control unit 14) starts the lockup engagement correction control for increasing and correcting the brake torque.
When the lockup clutch 20 inputs switching information from engagement to release via smooth lockup / off control, the engine controller (engine control unit 9) starts fuel cut recover control.
When the lockup clutch 20 inputs switching information from engagement to release via smooth lockup / off control, the brake controller (brake control unit 14) switches to lockup release correction control that reduces the brake torque correction amount. ..
Therefore, the secondary pressure Psec is limited so that the lockup clutch 20 becomes equal to or less than the upper limit hydraulic pressure in the switching determination region from engagement to release without changing the lockup release determination timing during coast deceleration due to the brake depressing operation. be able to. That is, the additional amount of the hydraulic characteristic of the secondary pressure Psec, which rises to the lockup release determination and decreases after the lockup release determination, is limited by the upper limit hydraulic pressure with the lockup release determination timing as the apex.

The control device for the belt-type continuously variable transmission of the present invention has been described above based on the first embodiment. However, the specific configuration is not limited to the first embodiment, and design changes and additions are permitted as long as the gist of the invention according to each claim is not deviated from the claims.

In the first embodiment, an example in which the belt type continuously variable transmission, the engine, and the brake are coordinated and controlled is shown. However, it may be a coordinated control configuration of the belt type continuously variable transmission and the engine, or it may be a coordinated control configuration of the belt type continuously variable transmission and the brake. Further, the secondary pressure limit control may be performed by the belt type continuously variable transmission alone.

In Example 1, an example is shown in which the control device of the present invention is applied to an engine vehicle equipped with a belt-type continuously variable transmission composed of a torque converter, a forward / backward switching mechanism, a variator, and a final deceleration mechanism. However, the control device of the present invention can also be applied to a vehicle equipped with a belt-type continuously variable transmission with an auxiliary transmission. Further, the vehicle is not limited to an engine vehicle, but can be applied to a hybrid vehicle equipped with an engine and a motor as a driving drive source, an electric vehicle equipped with a motor as a driving drive source, a fuel cell vehicle, and the like.

CVT belt type continuously variable transmission 1 engine (driving drive source)
2 Torque converter 20 Lock-up clutch 3 Forward / backward switching mechanism 4 Variator 42 Primary pulley 43 Secondary pulley 44 Chain belt 5 Final deceleration mechanism 6 Drive wheel 8 CVT control unit (transmission controller)
9 Engine control unit (driving drive source controller)
13 CAN communication line 14 Brake control unit (brake controller)

Claims (4)

A belt-type continuously variable transmission that is arranged between a drive source for traveling and a drive wheel and has a primary pulley, a secondary pulley, and a chain belt spanned over a sheave surface of the primary pulley and a sheave surface of the secondary pulley. Machine and
A transmission controller that controls the secondary pressure led to the secondary pulley of the belt-type continuously variable transmission based on the transmission input torque is provided.
The speed change controller is set to a lower hydraulic pressure as the vehicle deceleration increases during coast deceleration by depressing the brake , and the upper limit hydraulic pressure at which the sound vibration performance becomes an allowable level is calculated so as to be equal to or lower than the upper limit hydraulic pressure. A control device for a belt-type continuously variable transmission, which comprises a secondary pressure limiting control unit that limits the secondary pressure. In the control device for the belt-type continuously variable transmission according to claim 1,
The secondary pressure limit control unit calculates a lower limit hydraulic pressure that secures a clamping force for suppressing belt slip based on the transmission input torque, and when the lower limit hydraulic pressure is equal to or higher than the upper limit hydraulic pressure, the secondary pressure limit is equal to or higher than the lower limit hydraulic pressure. A control device for a belt-type continuously variable transmission characterized by limiting pressure. In the control device for the belt-type continuously variable transmission according to claim 2.
The secondary pressure limit control unit calculates a target hydraulic pressure that guarantees a predetermined safety factor based on the transmission input torque.
When the coast decelerates by depressing the brake, if the target hydraulic pressure larger than the lower limit hydraulic pressure is less than the upper limit hydraulic pressure, the secondary indicated pressure is calculated by adding the shift feedback hydraulic pressure to the target hydraulic pressure.
When the target hydraulic pressure is equal to or higher than the upper limit hydraulic pressure and the lower limit hydraulic pressure is less than the upper limit hydraulic pressure, the secondary indicated pressure is calculated by adding the shift feedback hydraulic pressure to the upper limit hydraulic pressure.
When the target hydraulic pressure is equal to or higher than the upper limit hydraulic pressure and the lower limit hydraulic pressure is equal to or higher than the upper limit hydraulic pressure, the secondary indicated pressure is calculated by adding the shift feedback hydraulic pressure to the lower limit hydraulic pressure. Control device for step transmission. In the control device for the belt-type continuously variable transmission according to any one of claims 1 to 3.
The driving drive source is an engine.
A torque converter arranged between the engine and the belt-type continuously variable transmission and having a lockup clutch,
The engine controller that starts fuel cut control when the accelerator foot release operation information is input,
It is equipped with a brake controller that starts correction control at the time of lockup engagement that increases and corrects the brake torque when the brake depression operation information is input.
When the lockup clutch inputs switching information from engagement to release via smooth lockup / off control, the engine controller starts fuel cut recover control.
The brake controller is characterized in that when the lockup clutch inputs switching information from engagement to release via smooth lockup / off control, it switches to lockup release correction control that reduces the correction amount of the brake torque. A control device for a belt-type continuously variable transmission.

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